1. Field of the Invention
This invention relates to improvements in methods and in apparatus for measurement of a constituent of a material utilizing near-infrared reflectance techniques.
2. Description of the Background Art
There is much prior art on the use of near-infrared radiation for the measurement of organic materials. Much of such art was pioneered by Robert D. Rosenthal and Trebor Industries, Inc. in their various instruments which provide near-infrared quantitative analysis. See, e.g. "An Introduction to Near Infrared Quantitative Analysis" presented by Robert Rosenthal from the 1977 Annual Meeting of American Association of Cereal Chemists, and Rosenthal U.S. Pat. Nos. 4,286,327, 4,404,642; 4,379,233; 4,487,278, all assigned to Trebor Industries, Inc. of Gaithersburg, Maryland.
Reflectance techniques have been used for analysis of components of grain, see for example, U.S. Pat. No. 3,776,642, Anson et al., assigned to Dickey-John Corporation which uses the near-infrared reflectance techniques and a rotating sample. The use of these near-infrared reflecance techniques requires the samples to be much more homogeneous than is possible with certain raw materials, e.g., ground sunflower seeds. Thus, large errors occur if conventional near-infrared reflectance measurement is attempted on ground sunflower seeds.
Nevertheless, there is a substantial need in the art to measure materials which are very non-homogeneous such as ground sunflower seeds. For example, ground sunflower seeds contain portions of the hull which differ greatly from the center portions of the hull seed, thus even the ground sunflower seed product is very non-homogeneous.
In the application of Rosenthal, et al., Ser. No. 726,658 filed Apr. 24, 1985, (now U.S. Pat. No. 4,633,087 issued Dec. 30, 1986) there is disclosed a means of measuring organic constituents in materials utilizing an interactance technique. In the application, the interactance technique utilizes a light beam source which must be in contact with the object being measured. A small amount of light that enters the object is scattered within the object and re-emits on the same side, but adjacent to the area of the object where the light contacted it. This interactance approach is best suited to materials which are pliable and at least moderately optically transmittive, for example, the human skin. This technique has also found application in a commercial machine for instantly analyzing the amount of fat in ground beef. Such machine is sold commercially under the trademark "The Lean Machine." However, until the present invention it was not possible to utilize the interactance tehniques of U.S. Pat. No. 4,633,087, for non-pliable materials or materials that have a high degree of opacity.